Active individuals, such as walkers, runners, and other athletes commonly use electronic devices to track both fitness data and route data. For example, a runner may utilize a health monitoring or measuring device to determine the distance that was traversed during a workout. One type of measuring device comprises an activity or distance measuring device which includes an accelerometer for determining the distance traversed by the runner. The accelerometer generates accelerometer data based on the detected movements associated with each stride taken by the runner. The accelerometer data is then processed to determine the distance traversed.
In some instances, the distance measuring device is further calibrated to ensure that the distance measuring device accurately determines the distance traversed by the user. One approach for calibrating the distance measuring device includes comparing a distance traversed as measured by the accelerometer to a distance traversed as measured using the global positioning system (“GPS”). The calibration process includes, processing the accelerometer data so that the distance traversed as measured by the accelerometer is equal to the distance traversed as measured by the GPS.
Global Positioning System calibration is typically useful and accurate; however, in some areas GPS signals are impacted by the topography of the landscape and cannot be reliably received by the typical consumer-level device. For example, in areas known as “street canyons” or “urban canyons” tall buildings can almost completely block the GPS signals from reaching a GPS receiver of the typical distance measuring device. Additionally, GPS data does not take into consideration altitude changes and/or other physiological parameters of the user which may effect stride length. As a result, in such an environment, GPS distance tracking is not the most accurate means for calibrating a distance measuring device. Accordingly, improvements in distance measuring devices and the processes for calibrating a distance measuring device are desirable.